A search for GMSB sleptons with lifetime at ALEPH

Abstract

A search for slepton production via the decay of pair-produced neutralinos has been performed under the assumption that the sleptons have observable lifetime in the detector before each decays to a lepton and a gravitino. Sleptons, neutralinos and gravitinos are particles predicted by the theory of supersymmetry, and are the supersymmetric partners of the Standard Model leptons, neutral bosons and of the graviton respectively. The search was performed in 628 inverse picobarns of data taken by the ALEPH detector at LEP centre-of-mass energies from 189 to 208 GeV. It was motivated by general predictions of Gauge-Mediated Supersymmetry Breaking (GMSB) models in which the lightest supersymmetric particle is always the gravitino. No evidence of the process was found. Model-independent cross-section limits are quoted as a function of neutralino mass, slepton mass and slepton lifetime in the case that the neutralino branching ratios to each slepton are equal at one third (the so-called slepton co-NLSP scenario, where NLSP stands for `Next-to-Lightest Supersymmetric Particle') and in the case that the neutralino decays exclusively to the stau (the stau-NLSP scenario). Excluded regions in the neutralino-stau mass plane are shown for four gravitino masses under model-specific assumptions.